How would you win the Sport Racing class/why am I wrong?

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Victor Bravo

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"Frontal area" or "flat plate equivalent area"? I believe there is a significant difference. Same principle as a round flying wire having ten times the drag of a streamlined flying wire of the exact same "frontal area".

The challenge is going to be putting the propeller far enough ahead of the engine to create a low drag shape. A very large spinner helps a lot, but you're still going to want that propeller two or three feet in front of the engine if you can find a way to do it.

At those power levels, RPM, and airflows, a tuned exhaust header and "bundle of snakes" is a big power boost. Sticking short exhaust stubs out the side like a Mustang probably ain't gonna cut it. Others here know far better than I, but I'm guessing there's 50-100 effective HP to be won or lost in exhaust tuning. If there wasn't, NASCAR vehicle designers would save the weight /heat/cost/complexity and not put them on race cars.
 

rv6ejguy

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These V8s would be turbocharged and with a PSRU so streamlining shouldn't be an issue and you wouldn't have stack exhausts either. Ideally a clean sheet design would route twin exhausts back to the rad duct to pull air through it and "pump" the duct.
 
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Riggerrob

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How long an extension shaft can you install before it flexes during high-G turns?
How long before you need an additional bearing at the prop hub?
 

Toobuilder

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As pictured above, A bare LS base V-8 is narrower, shorter, and less deep than a Lycoming 540. Getting one to fit in a streamlined cowl is not hard. Also noteworthy that the GP 5 engine pictured above is based on the "legacy" small block Chevy - the newer LS is even slightly smaller overall.
 

Toobuilder

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I'm half tempted to take a RV-4 kit, move the firewall back to the spar, move the pilot into the back seat, and hang a IO-720 on the mount. Would not be a Gold winner, but sure would be fun!

But the concept remains valid - Take something like a Casutt, scale the tubing appropriately, and hang the most HP you can afford on the thing. Or take an existing REALLY strong fuselage (like an Extra), put a fast wing and empenage on it (with the appropriate aero analysis), and hang a 1500 HP V-8 on the nose. Mixing and matching is what spawned the current Unlimited Gold winners - why not try it on a smaller scale?
 
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Deuelly

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It all sounds so easy when you put it like that. Would you be able to package a power plant like that in such a way that you could keep frontal area down below the two-seaters in the class?
When you're running 2 to 2.5 times the horsepower of the leaders in the class it probably wouldn't matter to much if your fuselage was narrower.

Brandon
 

Riggerrob

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I'm half tempted to take a RV-4 kit, move the firewall back to the spar, move the pilot into the back seat, and hang a IO-720 on the mount. Would not be a Gold winner, but sure would be fun!

But the concept remains valid - Take something like a Casutt, scale the tubing appropriately, and hang the most HP you can afford on the thing. Or take an existing REALLY strong fuselage (like an Extra), put a fast wing and empenage on it (with the appropriate aero analysis), and hang a 1500 HP V-8 on the nose. Mixing and matching is what spawned the current Unlimited Gold winners - why not try it on a smaller scale?
Most World War 2 fighters had their firewalls back near the main spar, just to balance their heavy engines.
 

Toobuilder

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How about the "composite" construction of the T-6 for a purpose built racer?: Welded tube Fwd fuselage to contain the pilot rollover structure, wing attach, gear legs and engine. Just aft of the pilot seat, add a bolt on tailcone/empenage of your choice (aluminum, carbon, wood, etc). You could have excellent crash protection and a really easy to analyze and fabricate primary structure, then have "relatively" easy to change aero structures.

Might not make the most efficient sport airplane, but would make a good race ship
 

Tiger Tim

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Welded tube Fwd fuselage to contain the pilot rollover structure, wing attach, gear legs and engine. Just aft of the pilot seat, add a bolt on tailcone/empenage of your choice (aluminum, carbon, wood, etc). You could have excellent crash protection and a really easy to analyze and fabricate primary structure, then have "relatively" easy to change aero structures.
I was thinking along the same lines, except maybe continue the tube structure all the way to the tail for even more aero tweaking flexibility. Seems to me that some of history’s most successful airplanes have been the ones that were relatively easily adaptable to new mods.
 

PMD

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I'm half tempted to take a RV-4 kit, move the firewall back to the spar, move the pilot into the back seat, and hang a IO-720 on the mount. Would not be a Gold winner, but sure would be fun!
Now, gasoline power plants are not something I spend much time with any more, but a 720? Come on, all it takes is the right cylinders and you can have a 780 with all stock Lyc parts, and a bit of cleanup should give a reliable 450 HP (co-inidentally smack on R-985 values). Then of course, there are the aftermarket liquid cooled cylinders that open up a LOT more potential at even lighter (OK, I know that is not a word normally associated with 720s) weights. Not sure one could reach 1,000 HP in this configuration, but should be able to come close in race trim = very short duty cycle.

If you still want to have the lump hung on the nose and 1500HP - maybe throw some cash as Andy Higgs and use his V12 diesel and have those Mustang-like little stacks in NA but no doubt just dummies when you use turbos to get to the required power. All of this doesn't take a lot of thinking out of the existing (small) box.

But the concept remains valid - Take something like a Casutt, scale the tubing appropriately, and hang the most HP you can afford on the thing. Or take an existing REALLY strong fuselage (like an Extra), put a fast wing and empenage on it (with the appropriate aero analysis), and hang a 1500 HP V-8 on the nose. Mixing and matching is what spawned the current Unlimited Gold winners - why not try it on a smaller scale?
I had a look through the Sonny's engines link from a few posts back. They/He have a 1,000 CID option in aluminum with all of the required power potential. Worth noting that a top fuel engine uses almost as much power just to drive the supercharger as we are discussing here. A 1k CID Mountain Motor should be able to knock out 3,000 turbocharged HP all day long, and with prices just over a hundred grand still leave a lot of money to develop the PSRU.

Now, to get collective heads out of box and some bodily orifice: why in the name of speed and efficiency would you want to put that thing on the nose??????? We all (yes, I readily admit to this same conflict) think the ultimate airplane happens to look just like a P51.
 

BJC

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We all (yes, I readily admit to this same conflict) think the ultimate airplane happens to look just like a P51.
Except the wing will be composite to achieve maximum laminar flow, likely will have a greater AR, and have better tips.


BJC
 

speedracer

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"Frontal area" or "flat plate equivalent area"? I believe there is a significant difference. Same principle as a round flying wire having ten times the drag of a streamlined flying wire of the exact same "frontal area".

The challenge is going to be putting the propeller far enough ahead of the engine to create a low drag shape. A very large spinner helps a lot, but you're still going to want that propeller two or three feet in front of the engine if you can find a way to do it.

At those power levels, RPM, and airflows, a tuned exhaust header and "bundle of snakes" is a big power boost. Sticking short exhaust stubs out the side like a Mustang probably ain't gonna cut it. Others here know far better than I, but I'm guessing there's 50-100 effective HP to be won or lost in exhaust tuning. If there wasn't, NASCAR vehicle designers would save the weight /heat/cost/complexity and not put them on race cars.
IIRC, Jon Sharps F1 Nemesis ran a 16" prop extension. They called it "the driveshaft".
 
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